Casting method and apparatus



July 5 1927' s. You'rsEYv CASTING METHOD AND APPARATUS I Original Filed Feb. 26. 1919 hetegy-Sheet 1 50 IZ' .1, l 94 W l/ /o i y 9.9

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Patented July 5, 192,7.

UNITED STATES-PATENT OFFICE.

FLOYD s. YoUzrsEY, or sr. LoUrs, Mrssormr, Assreivoa or y'oNuJ-raLr 'ro CLARENCE D. LUKENS, OF ST. LOUIS,MISSOURI.

CASTING METHOD AND APPARATUS.

v Application filed February 26, 1919, Serial No. 279,227. Renewed October 30, 1926.

This invention relates to methods and apparatus for casting metals under pressure.

In casting metals under pressure in metal molds or dies, which process is commonly known as die casting, the metal is forced into the mold either under the direct pressure o'f a' piston, or under the pressure of fluid, such as compressed air acting on the molten metal to force the same through the nozzle and into the die. f

While the fluid pressure method has many inherent advantages in that it eliminates the use of pistons which are usually subject to corrosive action of the molten metal, it introduces a valve or cut-off element between the melting pot and the nozzle, where the mass of molten metal acted upon by `the fluid pressure is sufficient to form a number of castings. Such a valve will not only be subject to the corrosive action of the molten metal, thereby leaking and causing the molten metal to squirt out of the leaks, but this` valve is liable to become clogged by freezing of the molten metal. The result, therefore, has been `that casting apparatus wherein the fhd pressure acts upon (a mass of molten metal sufficient to form a number of castings, has been unreliable in its operation. c

It is important inthe casting of metals under pressure in dies or metal molds that the cooling be as rapid as possible in order to prevent crystallization. This, however, enters another factor, namely the sudden cooling of the metal as it enters the mold, thereby causing vthe formation of imperfect castings.

before the mold is completely filled With the result that the finer recesses will not be filled, even after heavy pressure is applied, for the reason that the metal adjacent these recesses will have become cooled to such an extent that even abnormal pressures will not force the chilled metal in those recesses. It is, therefore, highly important that the flow of the metal into the mold be as rapid as possible and under as high an initial pressure as possible in order to secure complete filling of the mold.

One of the inherent characteristics of fluid operation is that where fluid is admitted under pressure to a chamber through an in- If the metal flows into the mold gradually, part of it is liable to cool or chill let connection, it takes an appreciable time for the fluid pressure tobecome established or risefto its maximum value. Accordingl Where the fluid pressure is applied to a bo y of molten metal to force it into the mold, and the metal begins to flow into the mold upon the application of the pressure, the pressure is not built up to a maximum until the mold is completely or nearly filled, with the result that the flow of the metal into the mold is not only slow, beginning at the lowest rate of flow, but the realy pressure of the fluid is not applied until the mold is entirely or nearly filled, with the result that the metal has become chilled before the same enters the finer recesses in the mold and the mold, therefore, will not be completely filled, thereby resulting in imperfect castings.

One of the objects of this invention, therefore, is to provide a method and apparatus 'for casting metals under pressure, in which the fluid pressure is applied to a quantity of molten metal sufficient to form a number of castings, andin which the metal, upon the application `of the fluid pressure, is

caused to flow through a normally open passage to fill the mold under pressure.

Another object is to provide a method and l apparatus for casting .metals under pressure, in which a time 'interval is provided between the application of the pressure and the filling ofthe mold, so that the casting pressure is established before the metal fills the mold. L

Another object is to provide amethod and apparatus for casting metals under pressure, in which the fluid pressure is applied to the molten metal and the nieta-l caused to flow 4into the mold, so as to quickly fill the same at high pressure and thereby produces per-l as to details of construction and further ob- `jects will appear from the detail descrip- Vno tion taken in connection with the accompanying drawings, in which:

Figure 1 is a longitudinal Vertical section showing a casting apparatus embodying this invention and illustrating the method of casting, embodying this invention; and

.Figures 2, 3, 4, 5 and 6 are views similar to Figure 1, but showing .different embodiments of and illustrating the method and apparatus embodying this. invention.

Referring to the accompanying drawings and more particularly to Figure 1, the mold may be of any suitable or usual construction, themold being preferably of sectignal form and one of such sections being shown at 50 and having the usual gate 53, the usual dowel pins 54 and the usual spiral cutting device 56.

In Figures 1 to 6 inclusive, are illustrated a numben of embodiments of apparatus embodying the casting of metal under pressure of a fluid. These figures also illustrate the method, although it will be understood that the method is independent of the particular mechanism employed and that the particular apparatus is only described for illustrating the several ways of carrying out the method embodying this invention.

Referring now to Figure 1, 80 designates a melting pot which may be in the form of.

a casting. The melting pot may be ribbed as shown at 81 so as to receive a fiame for maintaining the metal hot and in a molten condition. This 'melting pot may be supported on a frame in any suitable manner` The melting pot comprises a pressure chamber 82 ,and an auxiliary chamber 83 separated by a wall or partition 84. The pressure chanber 82 is arranged to receive the bulk of the metal and form a storage chamber; vin order to permit admission of the metal to this chamber, it is provided with. a yfunnel 85 opening into a port 86, closed by a valve 8 on a rod 88 passing through a stirrup 89, encircled by a spring 90, bearingvat one end against the stirrup and at its other end against a knob 91.

Opening into the pressure chamber is a fluid connection 92 having a valve casing 93' provided with a. compressed airinlet 94 and an exhaustor outlet 95. Mounted in the valve casing .is a valve 96 ada ted to connect lthe pressure chamber wit either the fluid supply 94or the exhaust 95. The funnel 8,5 as well as the fluid pressure connec` tion may be mounted on and attached to a cap plate. 97 secured by suitable screws98 tothe melting pot bod, to close the pressure chamber, it. bem un erstood that a seale connection is ma e.

Formed on the meltin pot and on the end of the auxiliary cham er body `is a nozzle 99 adapted to cooperate with a mold suclias ,50, and havin a. passage 100 opening from the top of e auxiliarychamber 83 at one end, the top wall 101 of ,this auxiliary chamber being inclined upwardly towards the passage 100. Arranged in the partition between the keeping this nozzle hot and, therefore, main-4 taining themetal in a fluid condition.

Assumin that the connected chambers have contained therein molten metal with the level of the metal in the auxiliary chamber .below the top thereof, that the pressure chamber is intconmunication with the air and that a mold is in position over and. in

cooperative relation with the nozzle; /gfthe operation will then be as follows:

The operator will move the' valve 96 so as to connect lthe pressure chamber with theV pipe 94 thereby applying fluid pressure on the molten metal in the pressure chamber.

As soon as the pressure is applied, the metal" is forced from the pressure chamber'into the auxiliary chamber.. It' will be noted,v

however, that the metal will not immediately, after the application of the fiuid pressure, flow from the nozzle and into the mold, for if it did, then the metall would enter the mold at a low pressure before the maximum In accordance with thisinvention, luponv and after application ofthe fluid pressurey to the molten meta in the pressure chamber (i. e., after opening of the valve. 96 to the pipe 94,) the metal will flow through the restricted aperture 102 into the auxiliarychamber 83. The -passage orA aperture 102 being, however, restricted, the flow of the metal from the pressure chamber to the yauxiliary chamber will be retarded; moreover, the metal vwill accumulate in `the :auxiliary chamber, .until it is filled, before the same enters the passage 'in the nozzle andbefore it enters andv fills the mold. This delaying action provides a time interval 'between the application of the pressure and the filling of the mold, and the parts are so proportioned that this time interval is sufi' cient to permit establishment of thepressure before the metal flows linto and fills the' ,mold yThe result is, therefore,- thatv when the metal Hows into the mold, it will be under its highest pressure, resulting not only velocity.

every recess in the mold is completely filled,V

thereby producing aV true casting corresponding to the mold cavity.

The restricted opening has also an additional important. function. It will be noted that when the metal issues through the opening under the pressure applied in the pres-v sure chamber, it will issue at an increasing Accordingly, a velocity head' is imparted to the metalowing from the pressure chamber through the nozzle, so that the metal enters the mold under a velocity head. The result is, therefore, that the metal enters the mold with a splash, -due to the accumulated velocity 'acquired by the accumu' lationl of the metal in the auxiliary chamber and its entrance into the mold through the` with the casting of metals, such as aluminum, that the passage between the pressure chamber and the mold will become clogged, thereby not only interfering with the operation in reducing the iow of the metal to the mold, but in some cases, even further chilling the metal at the clogged place and interrupting the operation altogether. Now it is well lnown that when a liquid flows along a passage'and an attempt is made to retard or arrest the flow of that liquid, a high pressure will be set up by the arresting of the flow, known in hydraulics as a water hammer. This pressure set up by arresting the flow is of great value compared to the initial pressure employed to cause the liquid to acquire the velocity. Accordingly, if the passage 100 or the gate in' the mold should become clogged, such` a high pressure will be set up that the passage will be cleared. Furthermore, upon completing the filling of the mold, the flow is arrested and where the metal acquires a velocity head in flowing to d the mold,l the said arresting by the filling of the mold will cause an abnormal'high pressure which applies a final high Ipressure to the metal in the mold and forces it into every fine recess, so as to complete the formation of .a thorough casting.

' tablishing causes the level of the metal in the pressure,l

After the mold has been filled, the valve 96 is moved to the position shown -in Figure 1, thereby-not' only cuttingoff the pressure on the molten metal in the pressure chamber,`l but exhausting the Huid therefrom and esatmospheric pressure. This chamber to rise and the metal in the auxilsprue cutter'56, it is found in practice that such a cutter is. really unnecessary, because the metal in the mold will become chilled to such an extent that when relieving the pressure in. the pressure chamber, a column of moltenmetal will drop from slightly above the heated nozzle, leaving a sprue of short length attachedto the casting which can be cut off' in any suitable manner.

In order to enhance thel water hammer action, it is necessary to increase the length of the column of moving liquid which acquires a velocity. This is laccomplished as shown in Figure. 2, by providing the restricted aperture 102 between the pressure and auxiliary 'chambers with a pipe 105 which opens from the pressure chamber 82 and has a series of convolutions 106 in the auxiliary chamber 83 in order to increase its length to a maximum. This pipe is placed in position by imbedding ,it in the core for the auxiliary chamber, and then casting the body of the pot thereon.

As shown in Figure 3, the pipe 105 is not only provided with convolutions 106 in the auxiliary chamber, but also with convolutions 108 in the pressure chamber, so as to still further lengthen the pipe and, therefore, the column of moving liquid. This pipe is imbedded in bothV cores for the pres' sure and auxiliary chambers.

In both Figures 2 and 3, after theapplication of the pressure, the molten metal is caused to fiow through a long pipe, thereby acquiring velocity, and any attempt to arrest the flow of the metal will cause a great increase in the water hammer pressure. It will, of course, be understood that the m'etal flows and accumulates in the auxiliary chamber 83, and after this chamber is filled, it flows to the nozzle. The operation is otherwise the same as in Figure l.

In Figures 1, 2 and 3, the mold is filled from the bot-tom, this invention is, however, applicable to filling the, mold from the top.\ This is shown in Figure 4, where the nozzle A99 is arranged at the bottomr of the pot and in which the nozzle passage 100 opens from a curved neck connection 109. The operation is very similar to the operation of the embodiment shown in Figure 1.

The metal after filling the auxiliary chamber will -fiow through the top thereof, through the passage 100 and into the mold 50 placed below the same. After the pressure in the pressure chamber is, however, reduced to atmospheric pressure, the lmetal level will drop in the auxiliary chamber and. this will return or tend to return the column of'molten metal in the passage 100, thereby l from the auxiliary chamber is taken from the top. It is desirable in some cases/to take this metal from the bottom which is the hot-y test part. This is shown in Figures 5 and 6, where similar parts are indicated'by' similar reference characters as in Figure 1. The

auxiliary chamber 83 has a connection to the nozzle passage 10() at 112 that is at the bottom of the chamber. In `the operation of this embodiment, the application of the pressure to the molten metal in-the pressure chamber will cause accumulation of metal in the auxiliary chamber before the metal begins to issue from the nozzle and till the mold. In this case, however, the metal is 5 taken from the bottom of the 'chamber where it is the hottest and where it is free from dross. A small vent is provided' at 113 for permitting venting ofthe air from the top ot the auxiliary chamber w-hile the metal ac- ,30 cumulates therein, to permit building up of the pressure and the velocity as is desirable. Where the vent is lemplo ed, the aperture closed by a plug 114 may e provided opposite the vent in order to permit formation of the vent and also opening of the same if it should become clogged. It will, of course, be understood that the vent is small compared to the passage 10U-112, and that in the actual operation practicall .all of the flow of the metal is throughft e large assage 10G-112, which metal is, therefidre, takei from the bottom of the chamber as desire In the embodiment shown in Figure 6, the

5 pipes 105, 106 and 108 are employed in order to increase the water hammer action but the openings of these pipes are arranged nearest they bottom of the chambers so as to take the.

metal from the lowest and hottest part of the pressure' chamber and deliver it to the lowest and hottest part of the auxiliary chamber: The general operation will, of

course, be the same as in the embodiment shown in Fi re 5. ,I

It will, therefore, be seen that theinvention accomplishes its objects. f The apparatus as a whole'is simple in construction and is lcapable of Idevelo ing great speed. The operating arm 7 2, or moving the mold sections and locate the mold sections over the nozzle,is operable by the -hand of the operator standing in front of the machine. The

tion carriers to open and close the mold sec.

valves and cut oi's is ,entirely eliminated,

thereby adapting the method and apparatus to/molten metal having highermelting oints and having great corrosive action suc for instance, as aluminum. On account of these characteristics of aluminum, it has heretofore been'difticult to cast aluminum in dies under pressure. With the method and apparatus embodying this invention, however, it is possible to form clean and smooth die castings of aluminum and metals having the higher melting points. The quick filling of the mold under high pressure and under a velocityhead is of special advantage in the casting of metals, such as aluminum, having a high conductivity of heat and, therefore, liable to cool very rapidly. This is also of special advantage when casting aluminum due to the fact that this metal must be cast at just as low a temperature as it will iow, otherwise it will become spongy and the castings will be hollow and weak.

It is obvious that various changes may be made in the details of the method and apparatus without departing from the spirit of this invention; `it is, therefore, to be understood that this invention is not to be limited to the specific details shown andl described.

Having thus described the invention, what is claimed is:

1. The method of casting, in which elastic fluid pressure Ais applied to the molten metal to force the same into the mold, characterized' by the feature that the applied pressure is establishedto its.maximum before the` metal fills .the mold.

2. The method of casting, in which elastic Huid pressure is-applied to the molten metal to force thesame into the mold, characterize'd b the A*feature that there is provided after t e application of the pressure, a time interval suiiicient to establish the applied pressure to its maximum before Athe metal fills the mold.

3. The method of casting, in which elastic, fluid pressure is applied to the moltenmetal y to'force the same into the mold, characterized `by'the feature that the metal flows to themold while the applied pressure is being established and fills the mold after thev (applied pressure attains its maximum.

4. The method of casting, in 4which elastic.

fluid pressure isapplied to the molten metal treadles 77 and 78, for shiftin the pivotal to force the same into tle mold, character y lconnection in order to move t e posltioned ized by the feature that the metal flows to being established to its maximum, an

the mold during a period sufficient to establish the applied pressure and fills the mold after the applied pressure attains its maxiltains its maximum.

6. The method of casting metals under pressure, comprising, applying elastic fluid pressure to the molten met-al, causing -the metal to flow While the applied pressure11 ils ing the mold under the established maximum pressure. l

7. The method of casting metals under pressure, comprising, applying elastic fluid pressure to the molten metal, causing the metal to flow to the mold during a period sufiicient to establish the applied pressure toits maximum, and filling the mold at the established maximum pressure.

8. The method of -casting metals under i A pressure, comprising, applying elastic fluid pressure to the molten metal, causing the metal to flow-to the mold during a period sufficient to permit building up of the applied pressure to its maximum, and lling the mold after the applied' pressure attains its maximum. i

9. The method of casting, in which fluid pressure is applied to the molten metal-to force the same into. the mold, characterized by the feature that the mold is filled under a. velocity head.

10. The method of casting, in which fluid pressure is applied to the molten metal to `force vthe same into the'mold, characterized by the'feature that there is, between the application of the pressure and the filling of the mold, a time interval sufficient to establish a `velocity head.

11. The method of casting, in whichfluid pressure yis applied to the molten metalto force the same into the mold, characterized by the feature that the metal flows to the mold during' a period sufficient to establish a velocity head so that the mold is filled un'. 4 der a pressure set up by arresting the flow of the metal.

12. Themethod of casting metals under pressure, comprising, applying fluid pres'- sure-to the molten metal, causing the metal to* low while a'velocity head is beinl established, andthereafter lling the mol under the established velocity head.

' 13'. The method "of casting metals under 'pre's'sure, comprising, applying fluid pres- 'sure' to the molten metal, causing the metal,

after :the 'application of the ressure, to flow "during a' time interval sufncie'nt to establish a velocity head, and thereafter suing the mold under the established velocity head.

14. .The method of casting metals under pressure, comprising, applying fluid pressure pressure, comprising, applying an increasing A elastic fluid pressure to the molten metal, causing the metal to flow, to the mold during a time interval sufficient to permit building up of thepressure to its maximum, and filling the mold after the applied pressure attains its maximum.

16. The method of casting, in which fluid pressure is applied to the molten metal to force the same into the mold, characterized bythe feature that the flow of the metal to the mold is delayed so'as to cause building up of the pressure before the mold is filled.

17. The method of casting, in which fluid pressure is applied to the molten metal to force the same into the mold, characterized by the feature that the flow of the metal to the` mold is delayed for a period suflicientl to establish the casting pressure before the mold is filled. v

18. The method of casting, in which fluid pressure-is applied to the molten metal to force the same into the mold, characterized by the feature that the flow of the metal 'to the mold is delayed but 'its velocity increased. so as to cause building up of a Y velocity head before the mold is filled.

by arresting the flow.

20. TheJ method of casting, in which fluid pressure is applied to the molten metalto force. the same into the mold, characterized by the feature that the metal flowing to the mold passes through a restricted vaperture. so as to delay its filling the mold unt-i1 the casting pressure is established.

21. The method of casting, in which fluid 12o pressure is applied to the moltenjmetal vto force the same into the-mold, characterized by the feature that' the metal flowing to the mold passesthrough a restricted aperture so as to establish a velocity head and delay filling of the mold until thevelocity head is established.

22. The method of casting metals under pressure, comprising, applying elastic fluid pressure to the molten metal, causing the -metal to accumulate While the applied presn sure, is being established to its maximum,

maximum, and filling'the mold under the established maximum pressure.

24. The method of casting metals under pressure, comprising, applying fluid pres sure to the molten metal, causing the metal to flow through a restricted aperture and accumulate for a`period sufficient to permit buildin up of the fluid pressure, and filling the mod underv the established pressure.

25. The' method of casting metals under pressure, comprising, applying fluid pressure to the molten metal, causing ithe metal to flow through a restricted aperture and ac uire momentum beyond the aperture, and' fi ling the mold under the velocity head so established.

26. The method of castin metals under pressure, comprising, applying fluid presy sure to the molten metal, causing the metal to pass through a long restricted passagato the mold, and delaying the filling of the mold until the casting pressure is established.

27. The method of casting metals under pressure, comprising, applying fluid pressure to the molten metal, causing the metall to pass through a long restricted passage to the mold, causing the metal to flow to the mold during a time interval, and then filling the mold. f

V28. The method of casting metals under pressure, comprising, applying fluid pressul'e to the molten metalcausing the metal to pass through a longrestricted passage to the mold in order to acquire momentum, and filling the mold under the velocity head so established.

29. The method of casting metals under pressure, comprising, applying elastic fluid pressure to a quantity of molten metal sufficient to form a number of castings, causing the metal upon application of the fluid pressure to flow to the mold While thev final pressure is being established to its maximum and ll the same to form a casting, and relieving the fluid pressure when the casting is formed'.

30. The method of casting, in which fluid pressure is applied to a quantity of molten metal sufficient to form a number of castings, characterized by the feature that the fluid pressure causes the metal to flow through a normally open long restricted passage to the mold and form the casting and'that the fluid pressure is relieved when the casting is formed.

v3l. The method of casting, in which themolten metal is maintained in a pressurechamber and a connected passage leadmg` to the mold, comprising, applying fluid pressure to the chamber, causing the metal to flow through the passage to the mold while the applied pressure is being built up, and filling the mold after the applied pressure has been establishedy to its maximum.

32. The method of casting, in which .the molten metal is maintained in a pressure chamber and a connected passage leading to the mold, comprising, applying fluid pressure to the chamber, delaying the flow of the metal to the mold until the casting pressure is established, and filling the mold under the f established casting pressure.

33. The method'of casting, in Which the molten metal is maintained in a pressure chamber and a connected passage leading to the mold, comprising, applying fluid pressure to the chamber, causing the metal to flow through the passage to the mold and accumulate momentum during such passage, and filling the mold under the velocity head so established.

34.. A casting apparatus, comprising, a pressure chamber for molten metal, means for applying elastic fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from-said chamber to said nozzle, adapted to cause building up of the applied pressure to its maximum before the metal fillsl the mold.

35. A casting apparatus, comprising, a pressure chamber for molten metal, means for applying elastic fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from said chamber to said nozzle, adapted to insure the establishment of the applied pressure to its maximum before the metal fills the mold.

36. A casting apparatus, comprising, a pressurechamber for molten metal, means for applying fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from said chamber to said nozzle, adapted to cause the metal in flowing to the mold to accumulate momentum and establish a Velocity head.

37. A casting apparatus, comprising, a pressure chamber for molten metal, means for applying fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from said chamber to said nozzle, adapted to cause the metal to flow to the mold for a distance and period sufficient to accumulate momentum and establish a velocity head.'k

38. A casting apparatus, comprising, a pressure chamber for molten metal, means for applying fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from said chamber to said nozzle, adapted to delay the flow of the metal to the mold in order to permit building up of the casting pressure.

.39. A. casting apparatus, comprising, a

Ilm

leading from said chamber,

pressure Chamber for molten metal, means for applying fluid pressure thereto, a nozzle adapted to receive a mold, and means for conducting the metal from saidl chamber to said nozzle, including a restricted aperture leading from said chamber, adapted to delay thepflow of the metal to the mold inf order to permit building up of the casting pressure.

4 0. A casting apparatus, comprising, a pressure chamber for molten metal, means for applying fluid pressure thereto, a nozzle adapted to receive a mold,`and means for conducting the metal from said chamber to said nozzle, including a restricted aperture adapted to cause the metal in flowing to the mold tol accumufor applying fluid pressure thereto,

late momentum and establish a velocity head.

41. A casting apparatus, comprising, a pressure chamber for molten metal, means a nozzle adapted to receive amold, and a long restricted Apassage for conducting the metal from saidchamber to said nozzle adapted to cause the metal in flowing to the mold to accumulate momentum and establish a ve.

locity head.

42. A casting apparatus, comprising, a pressure chamber adapted -to receive a sufficientquantity of molten metal to form a number `of castings, means for admitting and exhausting pressure fluid to and from said chamber,

' tic fluid pressure is applied to the molten metal to f'orce the same into the mold, characterized by the feature that there is prolvided' after the application of the pressure,

and a lnormally open restricted 4passage connecting said chamber with sald upon adm1ss1on of fluid, tov

acterized by the feature that there is provided after the application of the pressure,

a time interval sufficientto establish a high' velocity head in the metal flowing to the mold, and to build up the applied pressure to its maximum before the metal fills the mold and that the mold is filled under the established velocity head and at they maximum applied'pressure. l

45. The method of casting, in which elastic fluid pressure is applied to the molten metal' to force the same into the mold, characterized by the feature that a fluid head is established inthe molten metal before filling the mold adapted to apply a high casting pressure upon filling the mold.

46. The method of casting, in which elastic fluid pressure is applied to the molten metal to force the same into the mold, characterized by the feature that a lvelocity head is 'established'in a portion of the molten metal flowing to the mold before the mold is filled.

47. The method of casting, in which elastic fluid pressure is ap lied to the molten metal to force the same into the mold, characterized by the feature that a velocity head is established in a portion of the molten metal flowing to the mold before the mold is filled, while the fluid pressure on the metal attains its maximum, and that the mold is filled under the attained maximum fluid pressure and velocity head.

` In testimony whereof I aflix my signature this 10th day of Feb., 1919.

FLOYD S. YOUTSEY. 

